Abstract:

The Dead Sea is a deep hypersaline lake, characterized by a negative water balance and an overall stable thermo-haline stratification during summer months due to the warmer epilimnion (upper layer). Yet, the stable stratification is accompanied by small-scale instabilities that result in significant flux across the pycnocline. I will present observations from the Dead Sea and simulation results that highlight the major role of 'double-diffusion salt fingering' in the seasonal evolution of the water column's temperature, salinity and the precipitation/dissolution of halite. I will show how the 'salt fingers' that are typically symmetrical, become highly asymmetrical when salt precipitation/dissolution is involved. The net result is a strong, downward salinity flux that leads to the undersaturation of the epilimnion, while the hypolimnion becomes oversaturated and precipitates halite. These small-scale interfacial processes within deep, hypersaline water columns in warm and dry regions suggest a potential route toward the formation of thick halite layers found in the geological record.